1. Field of the Invention
The present invention relates to a communication network using code division multiplexing technology. The present invention can be applied to a communication network which performs peer-to-peer communications, for example.
2. Description of Related Art
Conventionally, peer-to-peer communication is known as one mode of using the Internet and other similar networks. Peer-to-peer may also be written as “P2P”, and is a communication system whereby information can be exchanged directly between a plurality of user communication terminals, via the Internet and other similar networks.
As is already known, technologies for connecting a user communication terminal to the Internet include, for example, ADSL (Asymmetrical Digital Subscriber Line), ATM-PON (Asynchronous Transfer Mode—Passive Optical Network), LAN (Local Area Network), or the like. The following references are amongst those which disclose communication technology of this kind.
(i) “xDSL/FTTH handbook”, ASCII Corp., p. 42-p. 45
(ii) Kiyoshi Yokota, et. al., “Optical access systems”, Oki Electric Technical Review, No. 182, Vol. 67, No. 1, April 2000, p. 19-p. 22
(iii) Yasuichiro Seto, ed., “Point diagram equations, Gigabit Ethernet™ handbook”, 1st Edition, 2nd Version, ASCII Corp., 1st May 2000, p. 53-p. 107
Peer-to-peer communication can be achieved by controlling packets by means of L2/L3 switches which use upper level layer. However, in a system for connecting a user communication terminal to a network, such as the Internet, by means of an ATM-PON or LAN system, as described above, one communication line is shared by a plurality of terminals. Therefore, it becomes necessary to guarantee bandwidth in order that P2P communication occupy a large communication capacity. In other words, if a plurality of communication channels are secured by bandwidth guarantee, P2P communication of large capacity become possible. However, in order to guarantee bandwidth, a new bandwidth guarantee control device is added, and/or the transmission capacity of the entire network must be increased, and the like. Therefore, the costs relating to the network architecture rise.
P2P communications can also be realized in a network using optical communication cables, by using optical wavelength division multiplexing technology. In this kind of network, P2P communication is achieved by adding a new wavelength channel for P2P communications. However, in this case, the components used in the optical wavelength division multiplexing are highly expensive, and so the costs relating to network architecture rise.
Moreover, high-capacity P2P communications can also be achieved by using code division multiplexing technology. However, in this case, bandwidth use efficiency becomes poor, due to the need for a channel for achieving synchronization between the terminals carrying out P2P communications. Therefore, the capacity of the communication circuit must be increased in order to secure a sufficient number of channels. For this reason, the costs relating to the network architecture rise.